Comb Duck/
Knob-billed Duck
Sarkidiornis melanotos

The unusual Comb drake with comb. The Comb Duck has two subspecies:
Sarkidiornis melanotos melanotos (above/immediately below)
which has grey flanks and comes from sub-Saharan Africa and tropical Asia and
Sarkidiornis melanotos sylvicola (further below)
which has black flanks and comes from tropical South America.

Comb duck (female doesn't have comb on bill).

Some class the South American, dark-flanked duck as a separate species: the Knob-billed Duck.